The Light and Dark of the Mangekyō Sharingan (万華鏡写輪眼の光と闇, Mangekyō Sharingan no Hikari to Yami) is episode 136 of the Naruto: Shippūden anime.

Synopsis

As Zetsu watches on, Itachi explains to Sasuke the secret behind the Mangekyō Sharingan, and the history of the Uchiha clan. Besides being able to tame the Nine-Tailed Fox, the Mangekyō will eventually rob the user of his eyesight and the only way to overcome this obstacle is to steal the Sharingan of that person's sibling. Sasuke retaliates against Itachi's assaults, but he is eventually pinned to a wall and has one of his eyes seemingly stolen by Itachi.